In the past, it has been known to use printed circuit electrical traces on a head suspension for disk drives. The head suspension itself is typically formed of steel, and serves as a supporting structure for the traces, separated therefrom by a thin insulator layer. The metallic nature of the supporting structure or layer affects both the differential mode impedance and the common mode impedance with respect to the electrical traces which are used to carry signals between a read/write head carried on the suspension and related circuitry off the suspension.
To address these issues, it has been known to remove one or more portions of the metallic layer to alter the impedances affecting the traces. Such removed portions have been informally known as xe2x80x9cwindows.xe2x80x9d
The present invention relates to an apparatus and method for controlling the common mode impedance, typically increasing the value thereof, while allowing independent control of the differential mode impedance. This is accomplished by providing at least some windows with electrically isolated islands or xe2x80x9cdoorsxe2x80x9d therein to enable an increase in the common mode impedance while maintaining a desired level of differential mode impedance.